redirfd -c nfile prog... has no portable
shell equivalent. Some shells provide the noclobber option for
a similar feature.

redirfd -x nfile prog... has no portable
shell equivalent.

Special fifo handling

The -n and -b options are especially useful with
named pipes.

Opening a fifo for reading, blocking if there is no writer:
redirfd -r nfifo prog...

Opening a fifo for reading, with instant success even if
there is no writer, and blocking at the first attempt to read from it:
redirfd -r -nb nfifo prog...

Opening a fifo for writing, blocking if there is no reader:
redirfd -w nfifo prog...

Opening a fifo for writing, with instant success even if
there is no reader:
redirfd -w -nb nfifo prog.... Warning:
the first attempt to write to the fifo will raise a SIGPIPE if there is
still no reader at that time. The named pipe semantics normally do not
allow a fifo to be open for writing without a reading end, and you
should know what you are doing if you're using redirfd
this way.